docs: def refs_to(cls, sha1, repo):
          """Returns all refs pointing to the given SHA1."""
          matching = []
          for refname in repo.listall_references():
              symref = repo.lookup_reference(refname)
              dref = symref.resolve()
              oid = dref.target
              commit = repo.get(oid)
              if commit.hex == sha1:
                  matching.append(symref.shorthand)
  
          return matching